Q: "unknown expression type 108" ?

Hi

appended below is a simple database schema (which may not
be a candidate for the next Nobel Prize for SQL Database
Design, but represents enough of a production
database to demonstrate the following problem).

And that is:

under 7.3 this statement:
SELECT foo_id, thingy_name, bar_name
FROM foo_view, bar
WHERE bar_id=foo_bar_id

produces the desired results.

This however:
SELECT foo_id, thingy_name, bar_name
FROM foo_view
INNER JOIN bar ON bar_id=foo_bar_id

produces

ERROR: ExecEvalExpr: unknown expression type 108

The latter statement does however work in 7.1.3 with no
apparent problems.

Question: what does "unknown expression type 108" mean and
why should it suddenly occur in 7.3? A bit of Googling
reveals the same message occurs when using subselects
in constraints, but that doesn't seem related to this case.

Ian Barwick
barwick(at)gmx(dot)net

-- sample DB for "unknown expression type 108" error

CREATE TABLE a_thingy (
a_id INT,
a_firstname VARCHAR(64),
a_lastname VARCHAR(64),
PRIMARY KEY (a_id)
);

CREATE TABLE b_thingy (
b_id INT,
b_name VARCHAR(64),
PRIMARY KEY (b_id)
);

CREATE TABLE bar (
bar_id INT,
bar_name varchar(64),
PRIMARY KEY (bar_id)
);

CREATE TABLE foo (
foo_id INT,
foo_a_id INT REFERENCES a_thingy NULL,
foo_b_id INT REFERENCES b_thingy NULL,
foo_bar_id INT REFERENCES bar NOT NULL,
PRIMARY KEY (foo_id),
CHECK((foo_a_id IS NOT NULL AND foo_b_id IS NULL) OR
(foo_b_id IS NOT NULL AND foo_a_id IS NULL))
);

CREATE VIEW foo_view AS
SELECT *,
CASE
WHEN foo_a_id IS NOT NULL THEN
(SELECT a_lastname || ', ' || a_firstname
FROM a_thingy
WHERE a_id=foo_a_id
)
WHEN foo_b_id IS NOT NULL THEN
(SELECT b_name
FROM b_thingy
WHERE b_id=foo_b_id
)
END
AS thingy_name
FROM foo;

INSERT INTO a_thingy VALUES
(1, 'John', 'Doe');

INSERT INTO b_thingy VALUES
(1, 'Megacorp');

INSERT INTO bar VALUES(1, 'squid');
INSERT INTO bar VALUES(2, 'octopus');

INSERT INTO foo VALUES (1,1,NULL,1);
INSERT INTO foo VALUES (2,NULL,1,2);

-- END